Overexpression of eukaryotic protein synthesis initiation factor 4E in HeLa cells results in aberrant growth and morphology

Proc Natl Acad Sci U S A. 1990 Nov;87(21):8212-6. doi: 10.1073/pnas.87.21.8212.

Abstract

Eukaryotic protein synthesis initiation factor 4E (eIF-4E) is a 25-kDa polypeptide that binds to the 7-methylguanosine-containing cap of mRNA and participates in the transfer of mRNA to the 40S ribosomal subunit, a step that is rate-limiting for protein synthesis under most cellular conditions. eIF-4E is the least abundant of the initiation factors, is present at approximately 10% of molar concentration of mRNA, and thus may serve as a site of regulation for the recruitment of mRNA into polysomes. Previous studies have indicated that phosphorylation of eIF-4E at Ser-53 is correlated with an increased rate of protein synthesis in a variety of systems in vivo and is required for eIF-4E to become bound to the 48S initiation complex. In this study we show that overexpression of eIF-4E in HeLa cells using an episomally replicating, BK virus-based vector leads to an unusual phenotype: cells grow rapidly, forming densely packed, multilayered foci. They progressively form syncytia, some containing as many as six nuclei, and ultimately lyse 1 month after transfection. Some of these properties are reminiscent of oncogenically transformed cells. Cells transfected with the identical vector expressing a variant of eIF-4E, which contains alanine at position 53 and thus cannot be phosphorylated at the major in vivo site, grow normally. Estimations using the Ala-53 variant or a bacterial chloramphenicol acetyltransferase reporter gene in the same vector indicate that the degree of eIF-4E overexpression is 3- to 9-fold more than the endogenous level. These results suggest that eIF-4E may play a key role in cell cycle progression.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Division
  • Chloramphenicol O-Acetyltransferase / genetics
  • Chloramphenicol O-Acetyltransferase / metabolism
  • Eukaryotic Initiation Factor-4E
  • Genetic Vectors
  • HeLa Cells / cytology
  • HeLa Cells / metabolism
  • Humans
  • Neoplasm Proteins / biosynthesis
  • Peptide Initiation Factors / genetics*
  • Peptide Initiation Factors / metabolism
  • Plasmids
  • Serine
  • Transfection

Substances

  • Eukaryotic Initiation Factor-4E
  • Neoplasm Proteins
  • Peptide Initiation Factors
  • Serine
  • Chloramphenicol O-Acetyltransferase